1. Field of the Invention
The present invention relates to an electric double layer capacitor.
2. Description of the Related Art
Conventionally, an electric double layer capacitor is known as a device, besides a chemical cell, which accumulates electrical energy. In the electric double layer capacitor, electrodes, which are made by an electrode material having a large specific surface area such as activated carbon, and an electrolyte, are used. Those electrodes are formed to face each other, and the electrolyte forms a dielectric layer called a Helmholtz layer. Since the electric double layer capacitor accumulates the electrical energy only by movements of ions in the electrolyte, the electric double layer capacitor has an advantage that it can charge or discharge the energy quickly compared with the chemical cell, in which an oxidation reduction reaction is present during the charge or discharge. Therefore, the electric double layer capacitor is used as a power supply for backup or auxiliary power of a cellular phone or a home appliance in recent years.
Typically, such electric double layer capacitor contains an electrode body, in which a separator is formed between a pair of the electrodes, and an electrolyte in a coin type metal can container. When the coin type capacitor is used as the power supply for the backup or auxiliary power, the capacitor is mounted on a printed circuit board by soldering. When mounting the capacitors, it is necessary to attach a terminal to the can container by welding etc. Therefore, there was a problem that a cost of parts and manufacturing are expensive. Moreover, when the can container is the coin type, there was a problem that a dead space tends to exist when mounting, because it is in a circular shape. Thus, the parts can not be mounted on the printed circuit board with high density.
Therefore, in recent years, an electric double layer capacitor using a concave-shaped container having a terminal for soldering is proposed (for example, refer to JP2001-216952). In such electric double layer capacitor, the concave-shaped container is made of ceramics or resins. After an electrode body and an electrolyte are contained in the container, a sealing plate is placed on the edge of an opening part of the container. Then, the opening part is sealed by adhering using brazing metals.
However, according to such conventional technology, since the sealing plate is provided on the edge of the opening of the container, the sealing plate and the container are easy to shift in a horizontal direction when sealing. As a result, a decline of the yield has been caused.